There is already known a semiconductor device having a mounting structure in which a semiconductor chip is mounted on an insulated substrate. An example of the structure is shown in FIG. 12. A semiconductor device 7 shown in this figure comprises a semiconductor chip 70 and an insulated substrate 71. The semiconductor chip 70 has a mounting surface 70a, which is connected with a surface 71a of the insulated substrate 71 via an adhesive 72 such as an epoxy resin. The semiconductor chip 70 has electrodes 70b faced onto and electrically connected with connecting terminals 71b of the insulated substrate 71. The insulated substrate 71 is a flexible film of e.g. a polyimide resin, and formed with a plurality of through holes 71c disposed in a grid pattern, each leading to one of the connecting terminals 71b. Via these through holes 71c, each of the connecting terminals 71b is electrically connected with a solder terminal 72 formed on the other side of the insulated substrate 71. The semiconductor chip 70 has side surfaces 70c surrounded by a protective resin 73 provided by e.g. an epoxy resin. The solder terminals 72 are disposed in a grid pattern correspondingly to the through holes 71c, and specifically called BGA (Ball Grid Array).
The protective resin 73 is formed by first applying the epoxy resin which is not yet fully hardened in thermosetting process, to enclose the side surfaces 70c of the semiconductor chip 70, and then heating at a temperature of 150° C. through 200° C. to complete the thermosetting process. The protective resin 73 shrinks as it is thermally set, and shrinks further as it is cooled down to the room temperature. The insulated substrate 71 also shrinks. However, an amount of shrinkage in the insulated substrate 71 is smaller than that of the protective resin 73, since the insulated substrate 71 is formed of polyimide resin which is superior to the protective resin 73 (epoxy resin) in terms of heat resistance and has a smaller coefficient of thermal shrinkage. In addition, since the insulated substrate 71 is flexible, the insulated substrate 71 is sometimes warped when the epoxy resin cools after the thermal setting. If the insulated substrate 71 is warped, the insulated substrate 71 can no longer sit horizontally, and when placed, the solder terminals 72 closer to the edge of the insulated substrate 71 are raised higher. This potentially causes an open circuit when the semiconductor device 7 is mounted onto a circuit substrate for example.
There is another problem. The adhesive 74 which connects the semiconductor chip 70 with the insulated substrate 71 is commonly provided by an epoxy resin. Therefore, again due to difference in the amount of thermal shrinkage between the insulated substrate 71 and the adhesive 74, interfaces of the adhesive 74 with the insulated substrate 71 and with the semiconductor chip 70 come under a certain strain. Therefore, according to the mounting structure as in the semiconductor device 7 shown in FIG. 12, in which an electrode bearing surface (the mounting surface) 70a is faced to the insulated substrate 71, the circuit element of the semiconductor chip 70 comes under the strain, and could be damaged.